Slight cleanup of fogging OnDestroy and some comments

Following b56f7f39d4 I dwelled in the fogging code. Some confusion could
have been avoided by some comments.
Also early-exit the loop to avoid doing un-necessary js->c++
transitions.

Reviewed By: Itms
Differential Revision: https://code.wildfiregames.com/D1737
This was SVN commit r22247.

binaries/data/mods/public/simulation/components/Fogging.js

@@ -182,30 +182,35 @@ Fogging.prototype.WasSeen = function(player)
 	return this.seen[player];
 };
 
-Fogging.prototype.OnDestroy = function(msg)
+Fogging.prototype.OnOwnershipChanged = function(msg)
 {
-	var cmpRangeManager = Engine.QueryInterface(SYSTEM_ENTITY, IID_RangeManager);
+	// Always activate fogging for non-Gaia entities
-	for (var player = 0; player < this.mirages.length; ++player)
+	if (msg.to > 0)
+		this.Activate();
+
+	if (msg.to != -1)
+		return;
+
+	let cmpRangeManager = Engine.QueryInterface(SYSTEM_ENTITY, IID_RangeManager);
+	for (let player in this.mirages)
 	{
+		if (this.mirages[player] == INVALID_ENTITY)
+			continue;
+
+		// When this.entity is in the line of sight of the player, its mirage is hidden, rather than destroyed, to save on performance.
+		// All hidden mirages can be destroyed now (they won't be needed again), and other mirages will destroy themselves when they get out of the fog.
 		if (cmpRangeManager.GetLosVisibility(this.mirages[player], player) == "hidden")
 		{
 			Engine.DestroyEntity(this.mirages[player]);
 			continue;
 		}
 
-		var cmpMirage = Engine.QueryInterface(this.mirages[player], IID_Mirage);
+		let cmpMirage = Engine.QueryInterface(this.mirages[player], IID_Mirage);
 		if (cmpMirage)
 			cmpMirage.SetParent(INVALID_ENTITY);
 	}
 };
 
-Fogging.prototype.OnOwnershipChanged = function(msg)
-{
-	// Always activate fogging for non-Gaia entities
-	if (msg.to > 0)
-		this.Activate();
-};
-
 Fogging.prototype.OnVisibilityChanged = function(msg)
 {
 	if (msg.player < 0 || msg.player >= this.mirages.length)

binaries/data/mods/public/simulation/components/Mirage.js

@@ -208,6 +208,7 @@ Mirage.prototype.UpdateTraders = function(msg)
 
 Mirage.prototype.OnVisibilityChanged = function(msg)
 {
+	// Mirages get VIS_HIDDEN when the original entity becomes VIS_VISIBLE.
 	if (msg.player != this.player || msg.newVisibility != VIS_HIDDEN)
 		return;